Field of the Invention
The present invention relates to a manipulation method of a magnetic particle so as to conduct chemical processes including a separation, an extraction, a purification and a chemical reaction of a target substance and further relates to a device for a magnetic particle manipulation applied thereto.
Description of the Related Art
Relative to a medical examination, food safety and hygienic control and monitoring of environment reservation and so forth, a target substance to be detected or subject to a chemical reaction must be extracted from the sample containing a variety of foreign materials. For example, such medical examination may have to conduct detection, identification and quantification of nucleic acids, proteins, saccharides, lipids, bacteria, viruses and radio-active substances and so forth included in the biological samples, e.g., blood, serum, cells, urine and feces and so forth, separated and obtained from plants and animals. In such examination, separation and purification of the target substance may be needed to eliminate a mal-effect relative to the background and so forth due to the foreign materials.
A method of separation and purification of the target substance in the sample using magnetic particles capable of specifically adsorbing the target substance has been developed and commercialized. Relative to such separation and purification using magnetic particles, firstly, the target substance is adsorbed on the surface of the magnetic particles having a particle diameter of approximately several μm and then after the foreign materials attached to the particle surface are washed away, the target substance is desorbed from the particle surface. For example, firstly nucleic acids are liberated from cells in blood when nucleic acids are extracted from blood. At this time, proteins in the cells are denatured using a strong protein denaturant such as a guanidium salt and so forth. The nucleic acids freed from the cells are specifically adsorbed on the silica coated magnetic particles. Following, the foreign materials and so forth attached on the magnetic particles are washed away with a cleaning solution and at last, the nucleic acids are eluted from the magnetic particles.
According to the separation and purification processes using such magnetic particles, a step of separating and recovering the magnetic particles in the liquid phase from the liquid phase by the magnetic manipulation and a step of dispersing the recovered magnetic particles in the liquid phase of the cleaning solution or the elution (liberation) and so forth are repeatedly conducted. Dispersion of the magnetic particles in the liquid phase is generally conducted by vibration and stirring by pipetting or vibrating with e.g., a Vortex mixer. The magnetic particles per se can be separated from the liquid phase by a magnetic manipulation using e.g., magnet so that a process of separation of solid and liquid by e.g., centrifugation can be eliminated and can facilitate to automatize such processes.
For example, a full automation device for a series of operations relative to separation and purification from adsorbing the target substance of the sample on the magnetic particles to cleaning and eluting thereof by conducting both recovery of the magnetic particles from the liquid phase and dispersion of the magnetic particles in the liquid phase by pipetting has been disclosed (e.g., Patent Document 1.) In addition, the Patent Document 2 discloses a method of suppressing a coagulation of the magnetic particles with a repulsive force of zeta potential under the condition in which an electric conductivity coefficient of the supernatant of the dispersion solution of the magnetic particles is not larger than 300 μS/cm.
As a method of separation and purification of the target substance using magnetic particles, the method using move of the magnetic particles in the device, in which liquids such as a cell lysis solution, a washing solution, an elution and so forth and an oil phase of oils and so forth are alternatively layered, is proposed. According to such method, the separation and purification of the target substance in a complete closed system can be conducted while suppressing any contamination. In addition, while continuously keeping such closed condition following the separation and purification, an operation of such as an analytical process can be conducted in the same device.
For example, the Patent Document 3 disclose that the gelled medium as the oil phase can be used relative to the device for the separation and purification, in which the aqueous phase and the oil phase are alternatively layered. According to such method, the magnetic particles in the aqueous phase moves to the inside of the layer of the gelled medium by a magnetic manipulation. Since the gelled has a thixotropic property, the magnetic particles can move inside of the gelled medium layer without damaging the gelled medium layer. On the other hand, the aqueous liquid attached to the magnetic particles cannot move into the inside of the layer of the gelled medium layer. Accordingly, due to a gellation of the oil phase, the magnetic particles adsorbing the target substance moving in the inside of the gelled medium layer can bring the solid-liquid separation (B/F separation) in reality and the separation and purification and recovery of the target substance can be conducted very efficiently.